Fuel cells utilize the reverse principle of the electrolysis of water, causing chemical reactions between hydrogen and oxygen, and producing electricity. Only water is theoretically discharged therefrom. Hydrogen is generally expressed as a fuel gas. Air is generally used as an oxygen supply source and expressed as an oxidant gas.
As such a fuel cell, a “Fuel Cell” disclosed in, for example, Japanese Patent Laid-Open Publication No. 2000-123848 is known. This fuel cell is configured to form a cell module by interposing an electrolyte membrane between an anode electrode and a cathode electrode and interposing the anode electrode and the cathode electrode between a first separator and a second separator via gaskets provided at the outer sides of the electrodes, respectively.
More specifically, a first flow path constituting a flow path of a fuel gas is formed on an internal surface of the first separator and a second flow path constituting a flow path of an oxidant gas is formed on an internal surface of the second separator, which supply a fuel gas and an oxidant gas to the middle electrolyte membrane, respectively.
Since an electric power obtained from a single cell module is very small, a plurality of such cell modules are stacked on one another to obtain a desired electric power. The first and second separators are separating members for preventing the leakage of a fuel gas or an oxidant gas into adjacent cells, thus being called as “separators.”
The first separator has on its internal surface the first flow path for a fuel gas and the second separator has on its internal surface the second flow path for an oxidant gas. It is required to provide the first and second flow paths with a plurality of very shallow grooves in order to effectively bring the gases into contact with the anode electrode and the cathode electrode.
The first and second separators each have, at one end a fuel gas supply hole and an oxidant gas supply hole for supplying a fuel gas and an oxidant gas to the first and second flow paths, respectively, and have, at the other end, a fuel gas discharge hole and an oxidant gas discharge hole, respectively. The first and second separators also have at the one end cooling water supply holes for letting in cooling water and have at the other end cooling water discharge holes.
The prevent inventors have made various attempts to produce a cell module by applying a liquid sealant instead of two gaskets to separators and interposing a membrane/electrode assembly consisting of an electrolyte membrane and electrodes between two separators, being confronted with a problem as described below.
FIGS. 18A and 18B illustrate a laminating process of two separators and a membrane/electrode assembly.
In FIG. 18A, a separator 203 applied with a sealant 202 is placed on a laminating station 201, a membrane/electrode assembly 206 consisting of an electrolyte membrane 204 and carbon electrodes 205, 205 attached to the opposite surfaces of the electrolyte membrane 204 is superimposed on the separator 203, and another separator 207 applied with a sealant 202 is superimposed on the membrane/electrode assembly 206, forming a lamination of the separator 203, membrane/electrode assembly 206 and separator 207, and thus producing a cell.
In FIG. 18B, the sealants 202, 202 applied to edge portions of the separators 203 and 207 are spread out by lamination. Since the separators 203 and 207 are warped toward each other, the outer thickness of the sealant 202 is t1 and the inner thickness thereof is t2 that is thinner than t1. The thinner the thickness of the carbon electrodes 205, 205, the thin part of the sealant 202 becomes thinner, preventing good sealing.
It is thus desired to improve a method of laminating a separator and a membrane/electrode assembly for fuel cells and an apparatus for laminating the same so as to obtain good sealing in fuel cells.